African penguins receive valentines from biologist Crystal Crimbchin at The California Academy of Sciences African penguin exhibit in San Francisco, Wednesday, Feb. 13, 2013. The valentines will be used as nesting material. less

African penguins receive valentines from biologist Crystal Crimbchin at The California Academy of Sciences African penguin exhibit in San Francisco, Wednesday, Feb. 13, 2013. The valentines will be used as ... more

An African penguin pulls a Valentine's Day card into its nest box at the California Academy of Sciences on February 13, 2013 in San Francisco. In honor of Valentine's Day, the colony of African Penguins at the California Academy of Sciences received heart-shaped red valentines with hand written messages from Academy visitors. less

An African penguin pulls a Valentine's Day card into its nest box at the California Academy of Sciences on February 13, 2013 in San Francisco. In honor of Valentine's Day, the colony of African Penguins at the ... more

Photo: Justin Sullivan, Getty Images

An African penguin pulls a Valentine's Day card into its nest... Photo-4195412.56841 - SFGate

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African penguins wait to receive Valentine's Day cards at the California Academy of Sciences on February 13, 2013 in San Francisco. The annual tradition promotes bonding between couples, the Academy said.

African penguins wait to receive Valentine's Day cards at the California Academy of Sciences on February 13, 2013 in San Francisco. The annual tradition promotes bonding between couples, the Academy said.

African penguins walk by a Valentine's Day card at the California Academy of Sciences on February 13, 2013 in San Francisco.

African penguins walk by a Valentine's Day card at the California Academy of Sciences on February 13, 2013 in San Francisco.

Photo: Justin Sullivan, Getty Images

African penguins walk by a Valentine's Day card at the... Photo-4195426.56841 - SFGate

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An African penguin walks out of its nest box after receiving valentines at The California Academy of Sciences African penguin exhibit in San Francisco, Wednesday, Feb. 13, 2013. The valentines will be used as nesting material. less

An African penguin walks out of its nest box after receiving valentines at The California Academy of Sciences African penguin exhibit in San Francisco, Wednesday, Feb. 13, 2013. The valentines will be used as ... more

Photo: Jeff Chiu, Associated Press

An African penguin walks out of its nest box after receiving... Photo-4195406.56841 - SFGate

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Taboola Gallery Frame Item-85307.56841 - SFGate

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An African penguin holds a valentine received from biologist Crystal Crimbchin at The California Academy of Sciences African penguin exhibit in San Francisco, Wednesday, Feb. 13, 2013.

An African penguin holds a valentine received from biologist Crystal Crimbchin at The California Academy of Sciences African penguin exhibit in San Francisco, Wednesday, Feb. 13, 2013.

Photo: Jeff Chiu, Associated Press

An African penguin holds a valentine received from biologist... Photo-4195407.56841 - SFGate

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Biologist Crystal Crimbchin hands out Valentine's Day cards to African Penguins at the California Academy of Sciences on February 13, 2013 in San Francisco, California.

Biologist Crystal Crimbchin hands out Valentine's Day cards to African Penguins at the California Academy of Sciences on February 13, 2013 in San Francisco, California.